The Effect of Temperature on the Rate of Photosynthesis.

The Effect of Temperature on the Rate of Photosynthesis

Jas Singh 10D

In all plants, a process called photosynthesis takes place. Photosynthesis is the process where by light energy is converted to chemical energy. It makes sugars and the by-product oxygen from CO2 and water, using the energy of sunlight. Photosynthesis occurs in chloroplasts. Here are the word and symbol equations for the process:

Carbon Dioxide + Water Gluecose + Oxygen

6CO2 + 6H20 C6H12O6 + 6O2

In my investigation, I am going to investigate the effect of temperature on the rate of photosynthesis. The plant I am gong to use is pondweed.

Prediction: I believe that the temperature surrounding the plant will have a significant effect on the rate of photosynthesis. I believe this because temperature affects all chemical reactions, and that photosynthesis should be no exception. I think that the rate of photosynthesis will steadily increase to begin with until around 30°C, where I think it will steady off. Then at 40°C I believe that the rate of photosynthesis will sharply decrease until it reaches zero. I think this because – as with all chemical reactions – enzymes are required. All enzymes have optimum levels at which they work best, and so I think that this point for the enzyme which acts on the plant during photosynthesis is around 40°C. From my own knowledge, I know that enzymes – after a certain point – will denature very quickly, and so that is why I have predicted that after the optimum point at 40°C the rate of photosynthesis will rapidly decrease until all the enzymes are denatured and so the rate drops to zero. Here is a sketch of what I believe that graph will look like:

I know that enzymes are chemicals that speed up, or catalyse, other reactions. However, the enzymes do not actually take place in the reaction or change it in any way except to make it happen faster. If an enzyme is boiled, it is very likely to denature, or basically die and stop working. This means their molecular structure is altered so that they can no longer work. This is why, if the temperature on the plant is too high, the rate of photosynthesis will rapidly slow down, as the enzymes all denature and so the reaction cannot take place. I also know from my own knowledge that when the temperature increases, the rate of reaction will also increase. I believe this will happen in the experiment as when particles are heated, they obtain more energy, and so the molecules of water in this reaction will move faster and so they will collide more frequently with the other molecules of carbon dioxide in the water (which was injected into the water in the form of Sodium Hydrogen Carbonate, or NaHCO3.) In turn, this will mean that the reactions will happen more frequently, and thus the rate of reaction will increase as a result. This relates to the enzyme-substrate reaction, as the enzymes will be moving faster and colliding into the molecules more frequently. Also, the rate of production I believe will peak at around the 40ºC, because I know that enzymes all have an optimum level in which they work at their most efficient and best. I am predicting that the temperature is 40ºC as it is probably just warm enough to produce as many bubbles of oxygen as possible, and just cold enough not to denature the enzymes.

Method:

The factor of this experiment that I am going to be changing is the temperature of the water, and thus the temperature of the plants surroundings.
To increase the temperature of the water, I will simply place a Bunsen Burner underneath the beaker in which the plant is, and wait until the temperature of the water is the desired one.
The temperature of the water will remain at the same level for quite a long time; long enough for me to carry out my readings. This is because I will fill the beaker with a ...